FoCal or USAF resolution chart for AF fine tuning

[alanlwilder]

I called Nikon in NY and they said after 2011 they stopped servicing that lens because parts are no longer available. I'll call APS Nikon in Morton Grove to see if they can check/adjust alignment since they serviced it 11/2020.

 

[DRwyoming]

I called Nikon in NY and they said after 2011 they stopped servicing that lens because parts are no longer available. I'll call APS Nikon in Morton Grove to see if they can check/adjust alignment since they serviced it 11/2020.

One other thought before you send your lens off. All the images you posted look to be a stop or so under exposed. The whites on the test charts aren't really white. Underexposure robs contrast and edge contrast is basically what we perceive as sharpness. You might try reshooting some of these images with the target well lit and using positive exposure compensation as needed to keep the bright whites white (without clipping the whites of course).

I'll often shine a bright light on my focus test targets but when testing a lot of lenses and striving for repeatability I'll illuminate the target with a diffused flash to make sure I've got plenty of consistent light on my target from test to test.

If better exposure doesn't show crisper images then I'd agree a good look by a service center is the way to go.

 

[alanlwilder]

Hey all, shot with my lens, attached is a full frame image at f/4 and 100% crops at the center, left edge and right edge. The camera was a D850, ISO 40. Test distance was the length of my basement of 29'. Unfortunately, the USAF charts are at least 50 yrs old and no longer pristine white. Adjusting the resolution #s for that distance, central resolution was 90 lp/mm ( just shy of group 2, pair 5) and the left or right edge was 75 lp/mm ( just shy of group 2, pair 4). Based in the acutance of these images, do you feel the lens is worth shipping to APS (Morton Grove, Il) for evaluation/adjustment? Nikon in NY won't touch it as they say parts are no longer available. If you feel service would be beneficial and APS declines, any suggestions on an independent service shop that could work on a lens this size? Any help would be appreciated. Thanks.

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Center:

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Right edge:

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Left edge:

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[kimball]

Hey all, shot with my lens, attached is a full frame image at f/4 and 100% crops at the center, left edge and right edge. The camera was a D850, ISO 40. Test distance was the length of my basement of 29'. Unfortunately, the USAF charts are at least 50 yrs old and no longer pristine white. Adjusting the resolution #s for that distance, central resolution was 90 lp/mm ( just shy of group 2, pair 5) and the left or right edge was 75 lp/mm ( just shy of group 2, pair 4). Based in the acutance of these images, do you feel the lens is worth shipping to APS (Morton Grove, Il) for evaluation/adjustment? Nikon in NY won't touch it as they say parts are no longer available. If you feel service would be beneficial and APS declines, any suggestions on an independent service shop that could work on a lens this size? Any help would be appreciated. Thanks.

Unfortunately an 8 second exposure is not useful for testing a 600mm lens. A car driving by your house will shake it. You walking around in your basement will shake it. These are not definitive tests.

Also, be aware that ISO 40 is an extended ISO on the D850, which means the body is just applying digital lightening darkening to achieve that ISO. Your base ISO is 64 on that camera.

Edit #2, to be more constructive: consider 1/600 (1/FL) to be a reasonable starting shutter speed for tests, hopefully at base ISO or at least a low ISO, like <= 400.

 

[alanlwilder]

There was no shake in the test. The shutter was opened for 10 seconds in the dark and exposure was made by turning the light switch on and off for a few seconds. This eliminated any chance of vibration from mirror slap or shutter vibration.

 

[kimball]

There was no shake in the test. The shutter was opened for 10 seconds in the dark and exposure was made by turning the light switch on and off for a few seconds. This eliminated any chance of vibration from mirror slap or shutter vibration.

I don't believe this is a good method for testing lenses.

Why not keep the lights on and shoot at a higher shutter speed? Why did you choose 8 seconds (not 10)? Why did you choose an extended ISO?

How did you decide how long to keep the light switch on? Why aren't you using your meter?

If you're worried about mirror slap and shutter shock, there are in-body settings to avoid those, namely Exposure Delay Mode and EFCS or completely silent shooting. Why not use them?

Not trying to be overly critical. Just trying to help you in pointing out that you're adding a lot of unnecessary variables that really bring into question your testing methodology.

 

[kimball]

Also: what setting was your VR on? I can't find that in the EXIF.

IMHO, you're better off using full daylight on a calm day, shooting your LensAlign target at 1/1000 or above, from a stable tripod, with VR off, wide open. Leave the ISO on auto and let it fall where it may (on a sunny day it shouldn't be crazy high at f/4). Employ exposure delay and EFCS/silent shooting.

Or shoot fully in live view. This is no longer a matter of AF fine tuning, but whether you've got a lens that needs to be repaired or not. Live view's contrast detection on a fixed, non-moving target should eliminated DSLR fine-tuning as a variable.

 

[alanlwilder]

This was a AFS Mk II version so there is no VR. Best focus was determined with manual focus, LiveView and focus peaking. I could re-shoot at ISO 64 but don't know if that would change anything. Keeping the shutter open for 10 seconds in the dark allows me to wait a few second before turning the light on and off to ensure there is no vibration to reduce any sharpness. Exposure was determined by placing the histogram peaks around the middle of the horizontal axis. The whole point of my method was to get the best possible sharpness so other could determine if the lens appears soft before I consider sending it out.

 

[Tom Reynolds]

I think Focal tests your lens sharpness.
I have not tried Focal outdoors because of the difficulty of getting the target vertical but on a wall in my house I test 500pfs successfully. (I purchased the Focal target.)

 

[kimball]

This was a AFS Mk II version so there is no VR.

Ah. I didn't catch that. This is a very old lens.

Still, it should be sharp.

Someone with the AFS Mk I version posted to DPReview that his lens was terribly blurry at f/4 but sharpened up by f/11 (!!). This might be worth testing before you send it in, as this shouldn't be happening:

Re: Nikon af-s 600mm f4d very soft at f4, only sharp by f11: Nikon SLR Lens Talk Forum: Digital Photography Review

Expert news, reviews and videos of the latest digital cameras, lenses, accessories, and phones. Get answers to your questions in our photography forums.

www.dpreview.com

original post here:

Nikon af-s 600mm f4d very soft at f4, only sharp by f11: Nikon SLR Lens Talk Forum: Digital Photography Review

Expert news, reviews and videos of the latest digital cameras, lenses, accessories, and phones. Get answers to your questions in our photography forums.

www.dpreview.com

 

[alanlwilder]

Lastly I'll post images of center crops for the 600/4D AFS Mk II at f/4 & f/5.6 as well as my 500/5.6E PF at f/5.6 for comparison (which probably performs close to the current 600/4E FL). While resolution is similar for all three, the 500/5.6E @ f/5.6 has a bit more bite in contrast than the 600 at f/4 but stopped down to f/5.6 the 600 comes very close to the 500/5.6. The main question I have is should the 600/4D AFS II have more contrast wide open than my sample? Stopped down a little it's pretty good.

600 @ f/4

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600 @ f/5.6

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500 @ f/5.6

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[Drbobcameraguy]

I agree - unless there is something in your technique that is allowing vibration to cause the softness. That lens should be much sharper.

Working with Nikon for service, be sure you send them your test images including the LensAlign samples. Let them see that it's not sharp so they don't think it's a calibration issue. You might send your camera body as well. I know it's a nuisance, but it gives them everything needed to assess.

I'm assuming you have your gear insured. Check to verify, but most policies cover losses if gear is being shipped. There is no need to buy extra insurance for your gear to be shipped - and on that lens it could save you $100.

Yes it is a nuisance but well worth the trouble. Even for 3rd party lens issues. I sent my d7200 and my Sigma 150-500 to sigma because after they replaced the focus motor board it wasn't as sharp as before. When I received them back it was sharper than ever. I was honestly impressed. Both those pieces are long gone but a good lesson learned.

 

[Drbobcameraguy]

Lastly I'll post images of center crops for the 600/4D AFS Mk II at f/4 & f/5.6 as well as my 500/5.6E PF at f/5.6 for comparison (which probably performs close to the current 600/4E FL). While resolution is similar for all three, the 500/5.6E @ f/5.6 has a bit more bite in contrast than the 600 at f/4 but stopped down to f/5.6 the 600 comes very close to the 500/5.6. The main question I have is should the 600/4D AFS II have more contrast wide open than my sample? Stopped down a little it's pretty good.

600 @ f/4
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600 @ f/5.6
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500 @ f/5.6
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I have to agree with Steve. Your lens appears sharper in the corners than the center by far in your previous post of crops. The one where you show center and right and left corners. The center should be as sharp if not sharper than the corners as I understand it.

 

[alanlwilder]

Not sure what you seeing but in all my posted images the center target was sharper than the edge shots. Stopping down to f/5.6 adds more contrast similar to the 500/5.6E PF.

 

[alanlwilder]

Based on comments, especially from Steve Perry, I've decided to return the lens to the seller. Resolution of the lens is quite good even at f/4 but contrast is sub-par wide open by today's standards for high MP digital cameras. Given that it's contrast improves significantly by stopping down just one stop with f/8 as optimal, I suspect it performs close to expected since the optical design dates back to the mid-1990's when film was their main format. Also it's interesting to note that according to FoCal's database on IQ, the typical 600/4 AFS II performance wide open scored 63/100 while the G and FL version scored 80/100 and 89/100 respectively. This seems about consistent with my lens.

 

[Steve]

Based on comments, especially from Steve Perry, I've decided to return the lens to the seller. Resolution of the lens is quite good even at f/4 but contrast is sub-par wide open by today's standards for high MP digital cameras. Given that it's contrast improves significantly by stopping down just one stop with f/8 as optimal, I suspect it performs close to expected since the optical design dates back to the mid-1990's when film was their main format. Also it's interesting to note that according to FoCal's database on IQ, the typical 600/4 AFS II performance wide open scored 63/100 while the G and FL version scored 80/100 and 89/100 respectively. This seems about consistent with my lens.

That's probably a good decision. As you say, it gets better as you stop down, but just doesn't seem to keep up with today's tech.

 

[Hermann]

Resolution of the lens is quite good even at f/4 but contrast is sub-par wide open by today's standards for high MP digital cameras. Given that it's contrast improves significantly by stopping down just one stop with f/8 as optimal, I suspect it performs close to expected since the optical design dates back to the mid-1990's when film was their main format.

I still have an old 4/300, the screwdriver version. On modern digital bodies the contrast isn't very good wide open, presumably because the coatings aren't really up to scratch compared to modern coatings. Still like that old lens, however, must be one of the toughest lenses I own.

Hermann

 

[bjanes]

Hi Steve, I bought it from a seller on FM who provided documentation from Nikon APS (Morton Grove, IL) that shows the lens had a complete service 11/2020 including motor replacement, element cleaning, bayonet mount replacement and general CLA. Do you suggest sending it back to them or Nikon in NY? If so what should I ask them to do?

I've used Nikon APS in Morton Grove with decent results, but I had a 80-400 VR 2 repaired by them for impact damage at a cost of about $500. I calibrated the repaired lens with Reikan Focal and astigmatism was off the chart and focus quality was not good. I then sent the lens to Nikon in New York and retesting showed markedly improved results. From this experience, I agree with Steve that it would be a good idea to send the lens to Nikon.

Jim Kasson has published an excellent article on testing for lens tilt and centering and you might consider using this screening method.

Cheers,

Bill

 

[alanlwilder]

Nikon in NY won't touch the lens as they stopped servicing that model in 2011 due to parts no longer available. The reasoning is that if anything happens when they open it up and a part is needed as a result of their attempt, you're SOL. Easier to return to seller.

 

[alanlwilder]

As a follow up, here is a crop comparison of the previously owned 600/4D AFS II and the recently acquired 600/4E FL shot wide open on the LensAlign MkII using a D850. Obviously the FL version has better contrast/IQ but the spoke target on the left appears similarly sharp but of much less contrast. Not shown are the results stopped down to f/5.6 where contrast substantially improves on the 600/4D AFS II leading me to believe spherical aberration is the main culprit.

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